Cardiopulmonary resuscitation (CPR) is a well-known and valuable method of first aid used to resuscitate people who have suffered from cardiac arrest. CPR requires repetitive chest compressions to squeeze the heart and the thoracic cavity to pump blood through the body. Artificial respiration, such as mouth-to-mouth breathing or a bag mask apparatus, is used to supply air to the lungs. When a first aid provider performs manual chest compression effectively, blood flow in the body is about 25% to 30% of normal blood flow. However, even experienced paramedics cannot maintain adequate chest compressions for more than a few minutes. Hightower, et al., Decay In Quality Of Chest Compressions Over Time, 26 Ann. Emerg. Med. 300 (September 1995). Thus, CPR is not often successful at sustaining or reviving the patient. Nevertheless, if chest compressions could be adequately maintained, then cardiac arrest victims could be sustained for extended periods of time. Occasional reports of extended CPR efforts (45 to 90 minutes) have been reported, with the victims eventually being saved by coronary bypass surgery. See Tovar, et al., Successful Myocardial Revascularization and Neurologic Recovery, 22 Texas Heart J. 271 (1995).
In efforts to provide better blood flow and increase the effectiveness of bystander resuscitation efforts, various mechanical devices have been proposed for performing CPR. In one variation of such devices, a belt is placed around the patient's chest and an automatic chest compression device tightens the belt to effect chest compressions. Our own patents, Mollenauer et al., Resuscitation device having a motor driven belt to constrict/compress the chest, U.S. Pat. No. 6,142,962 (Nov. 7, 2000); Bystrom et al., Resuscitation and alert system, U.S. Pat. No. 6,090,056 (Jul. 18, 2000); Sherman et al., Modular CPR assist device, U.S. Pat. No. 6,066,106 (May 23, 2000); and Sherman et al., Modular CPR assist device, U.S. Pat. No. 6,398,745 (Jun. 4, 2002); and our application Ser. No. 09/866,377 filed on May 25, 2001, our application Ser. No. 10/192,771, filed Jul. 10, 2002 and our application Ser. No. 12/726,262, filed Mar. 17, 2010 show chest compression devices that compress a patient's chest with a belt. Each of these patents or applications is hereby incorporated by reference in their entireties.
Since seconds count during an emergency, any CPR device should be easy to use and facilitate rapid deployment of the device on the patient. Our own devices are easy to deploy quickly and may significantly increase the patient's chances of survival.
One important aspect of such devices is the need for small, powerful yet reliable power supply to power the device. It is not uncommon for CPR to be administered for at least thirty minutes. Thus, the power supply must be capable of delivering sufficient energy to the motor driving the compression device for at least that length of time. Moreover, the power supply must be relatively light weight, so as to enhance portability of the chest compression device, yet it must deliver its power for an extended period of time without significant voltage or current drop off to ensure consistency of compression throughout the treatment period.
Since a mechanical compression device is often transported to a remote location, the device must be robust enough to withstand not only the jolts and jostles of transportation, but also the shock of being dropped or roughly handled when being placed into position to accept a patient. For example, under such use the battery pack powering the device may become disengaged from the device when it is dropped or jostled. Such disengagement will require, at the least, re-insertion of the battery in the battery compartment, and may even cause damage to the battery requiring replacement of the battery.
Even if the battery is not completely disengaged, the battery may become loose in the battery compartment. This may cause a disconnection of the battery during use which will stop operation of the mechanical compression device, and require quick troubleshooting by the user of the device to determine why the device is no longer operating. Such a loose engagement may also increase the resistance of the electrical connection between the battery and the device. This increased resistance may lead to a decreased battery capacity, requiring compressions to be halted for replacement of the battery in a shorter than expected time.
What has been needed, and heretofore unavailable, is a light weight, reliable battery pack having a latch mechanism capable of retaining the battery within a device to be powered even when exposed to forces resulting from jolts and other trauma occurring during transportation or rough handling of the powered device as it is carried to a patient or when the patient is placed on the device. Such a latch must be reliable and easy to engage and disengage to facilitate rapid insertion and removal of the battery from a battery compartment. It would also be useful to provide a visual indication that the battery latch if fully engaged with the battery compartment. The present invention satisfies these, and other needs.